1. Field of the Invention
The present invention relates to a stacked solid electrolytic capacitor used in various electronic devices.
2. Description of Related Art
The demand for reliable capacitors having lower impedance, and smaller and thinner profiles has grown steadily in recent years as a result of ever increasing higher CPU speeds, higher integration, and space saving requirements in motherboards. Conventional approaches for meeting this demand include connecting in parallel multiple stacked ceramic capacitors.
Smaller, thinner stacked solid electrolytic capacitors having greater capacitance and lower impedance are being developed in order to realize large capacitance and low impedance, as achievable when several tens of stacked ceramic capacitors can be made up for by one single capacitor, having superior thermal resistance. To meet the above requirements, it has been proposed to achieve greater capacitance and lower ESR (equivalent series resistance) by stacking in parallel stacked solid electrolytic capacitors (for instance, Japanese Unexamined Patent Application Publication No. 2006-093343).
As disclosed in Japanese Unexamined Patent Application Publication Nos. 2004-281515 and 2007-165777, conduction in stacked cathode sections has been ensured in recent years by dipping the entire surface of the cathode sections of a stack of solid electrolytic capacitor elements in a conductive paste, followed by curing, with a view to reducing interface resistance, simplifying manufacture, and reducing thickness.
In conventional solid electrolytic capacitor element stacks, however, the desired ESR reduction afforded when the number of stacked layers increases by virtue of formula (1) below cannot be realized, and thus the advantages of stacking cannot be exploited, even when using technologies for connecting anodes in the stack, or when the entire surface of the stack cathode sections is coated with a conductive paste.1/R=1/R1+1/R2 . . . 1/Rn  (1)
R: ESR of the stacked solid electrolytic capacitor
R1, R2 . . . Rn: ESR of individual stacked solid electrolytic capacitors